The Nimda worm is a worm that spreads itself through various means, including email, and infects local files and files on network share on Windows 95, Windows 98, Windows ME, Windows NT and Windows 2000 platforms. Nimda attacks IIShttp servers and also seeks backdoors left by Trojans such as Sadmind and Code Red.
Nimda uses .htm files and the MAPI service to obtain email addresses to which it then sends itself as a MIME-encoded email attachment every ten days. Nimda can also infect a clientcomputer browsing an infected IIS web server, using the client web browser's javascript capabilities. Research Nimda